Pure silver is too soft and can easily become damaged or scratched. It is therefore most commonly combined with copper to create a more durable alloy.
Sterling silver is the most popular alloy containing 92.5% silver and 7.5% copper. While this small percentage of added copper does not affect the silver color, it greatly improves its durability and hardness.
Also to note, is that this addition of copper has little effect on the jewelry's value. Rather it is more directly related to the labor and time involved in the making, and the intricacy of a particular piece.
Sterling silver can be identified by a "quality" or "fineness" marking stamp or engraving which is required by law. Generally you would notice the ".925" mark (denoting 92.5%) on smaller objects such as jewelry. Larger items, such as flatware, trays, and tea sets, might be stamped or engraved with "sterling" or "sterling silver," etc., as well as the manufacturer's logo or trademark.
Caring for Silver
To keep your jewelry free of tarnish, frequent cleaning in a simple dilute solution of mild dishwashing liquid and water is best. Rinse and dry thoroughly and store in a dry container. The presence of moisture can act as a catalyst and will promote tarnish. If possible, store your jewelry in a zip-loc plastic bag with anti-tarnish paper.
Light tarnish or oxidation film can be removed with silver polishing cloths available at major supermarkets, hardware stores or jewelry shops.
Heavy tarnishing will require the use of commercially available polishing creams, or dip liquids. Do use care with these, limiting the exposure of gemstones to silver cleaners as they may contain chemicals that can harm certain gemstones. Always rinse and dry jewelry thoroughly with a soft cloth making sure no residual cleaner remains.
While cream and dip liquid polishes will most likely remove tarnish and oxidation from your jewelry, they will almost certainly remove any decorative oxidation designs and patinas as well. Therefore it is best to keep these items free of tarnish through proper storage and the use of cleaning cloths.